Code Snips Web Development Snippets

Here is a collection of handy snippets for VB developers who may be in the process of transitioning to C#.

Comments

Single line

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//Comment

Multi-line comments

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/* This section
is commented */

XML Comments

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/// My XML Comment

C# Data Types

• byte
• sbyte
• int
• uint
• short
• ushort
• long
• ulong
• float
• double
• decimal
• bool
• char
• string
• object

C# Variable Declaration

public | protected internal | protected | internal | private type variable-name

Example

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private string str_MyVar = "My Value";

C# Arrays

Single Dimension

<type>[] <name> = new <type>[ArraySize];

Example

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string[] str_Array = new string[2];

Multi-dimensional

<type>[,] <name> = new <type>[ArraySize,ArraySize];

Example

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string[,] str_MultiArray = new string[5,4];

ArrayList

ArrayList resizes dynamically. As elements are added, it grows in capacity to accommodate them. It stores a collection of elements of type object; therefore casting is necessary. You also need to reference System.Collections.

Example

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ArrayList list = new ArrayList();
list.Add("One");
list.Add("Two");
list.Add("Three");

Initialize Array

<type>[] <name> = new <type>[ArraySize] {<value1>, <value2>, … , <valueN>};

Example

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int[] int_MyValues = { 1, 2, 3, 4, 5 };

Change Size of Array

<type>[] <name> = new <type>[ArraySize];

Example

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Array.Resize(ref int_MyValues, 10);

Operators

Arithmetic

+ (Addition), – (Subtraction), * (Multiplication), / (Division), % (Modulus)

String Manipulation

• Concatenation: str_WelcomeText = “My name is ” + “Fred Blogs”;
• .Substring(<start>,[<length>])
• .Trim() <trims from beginning & end of string>
• .TrimEnd([<char array>])
• .TrimStart([char array])
• .ToLower() <to lower case>
• .ToUpper() <to upper case>
• .Replace(<find>,<replace>)
• .Equals(<expression>) <6 available overloads>
• .Contains(<string>)
• .Join(<seperator>,<value>,[<count>])
• .Compare(<string1>,<string2>,[<ignore case>]) <7 overloads available>
• .Copy(<string>)
• \’ – single quote, needed for character literals
• \” – double quote, needed for string literals
• \\ – backslash
• \0 – Unicode character 0
• \a – Alert (character 7)
• \b – Backspace (character 8)
• \f – Form feed (character 12)
• \n – New line (character 10)
• \r – Carriage return (character 13)
• \t – Horizontal tab (character 9)
• \v – Vertical quote (character 11)
• \uxxxx – Unicode escape sequence for character with hex value xxxx
• \xn[n][n][n] – Unicode escape sequence for character with hex value nnnn (variable length version of \uxxxx)
• \Uxxxxxxxx – Unicode escape sequence for character with hex value xxxxxxxx (for generating surrogates)

String Escape Characters

Assignment

• = (Equals)
• += (Addition)
• -= (Subtraction)
• *= (Multiplication)
• /= (Division)
• %= (Modulus)
• &= (And)
• |= (OR)
• ^= (Exclusive OR)
• >>= (Right Shift)
• <<= (Left Shift)
• == (Equal To)
• ! = (Not Equal To)
• < (Less Than)
• > (Greater Than)
• <= (Less Than or Equal To)
• >= (Greater Than or Equal To)
• is
• as

Comparison

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if (person is Employee)
{
   // Do employee stuff
}
else if (person is Customer)
{
   // Do customer stuff
}

Logical

• & (And)
• | (Or)
• ^ (Xor)
• && (AndAlso)
• || (OrElse)

Error Handling

try
{
//<statements that may cause an error>;
}
catch(Exception ex)
{
//<statements to use when an error occurs>;
}
finally
{
//<statements to use no matter what happens>
}

Example (from MSDN)

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try
{
   myCommand.Connection.Open();
}
// Catch the exception as e and pass it to the ShowErrors routine.
catch (SqlCeException e)
{
   ShowErrors(e);
}

// Error handling routine that generates an error message
public static void ShowErrors(SqlCeException e)
{
   SqlCeErrorCollection errorCollection = e.Errors;

   StringBuilder bld = new StringBuilder();

   Exception inner = e.InnerException;

   if (null != inner)
   {
      MessageBox.Show("Inner Exception: " + inner.ToString());
   }

   // Enumerate the errors to a message box.
   foreach (SqlCeError err in errorCollection)
   {
      bld.Append("\n Error Code: " + err.HResult.ToString("X"));
      bld.Append("\n Message   : " + err.Message);
      bld.Append("\n Minor Err.: " + err.NativeError);
      bld.Append("\n Source    : " + err.Source);

      // Enumerate each numeric parameter for the error.
      foreach (int numPar in err.NumericErrorParameters)
      {
         if (0 != numPar) bld.Append("\n Num. Par. : " + numPar);
      }

      // Enumerate each string parameter for the error.
      foreach (string errPar in err.ErrorParameters)
      {
         if (String.Empty != errPar) bld.Append("\n Err. Par. : " + errPar);
      }

      MessageBox.Show(bld.ToString());
      bld.Remove(0, bld.Length);
   }      
}

Conditional Branching

If Else

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if(expression)
{
   <statement 1>;
}
else
{
   <statement 2>;
}

C# version of IIF()

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variable == ?true:false;

For Loop

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for(statement)
{
   <statement>;
}

For Each Loop

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foreach(<variable> In <object>)
{
   <statements>;

   [break];
   [continue];
}

While Loop

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while(<expression>)
{
   <statement>;
}

Do-While Loop

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do
{
   <statement>;
} while <expression>;

Select Case Statement

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switch(<expression>)
{
   case <literal or type>:
      <statement>;
      <break>;
   case <literal or type>:
      <statement>;
      <break>;
   default:
      <statement>;
      <break>;
}

Else If

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if (Condition_1)
{
   // Statement_1;
}
else if (Condition_2)
{
   // Statement_2;
}
else
{
   // Statement_n;
}

Functions & Sub Routines

Function Structure

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<private, public, protected, internal> [static] <ReturnType> <Function_Name>;([Parameters])
{
   //body of the function;
   return <ReturnType>;
}

Sub Routine Structure

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<private, public, protected, internal> void  <method_name>([Parameters])
{
   //body of the procedure;
}

Control Functions

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void MyButton_Click (Object sender, EventArgs e)
{
   // When the button is clicked do stuff
}

<asp:Button id="MyButton" Text="Click Me" OnClick="MyButton_Click" 
runat="server" />

Class Structure

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public class <Class_Name>
{
   //body of class
}

Base Class Idea
http://www.4guysfromrolla.com/articles/041305-1.aspx

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public class MyBaseClass : System.Web.UI.Page
{
   protected override void OnLoad(EventArgs e)
   {
      // ... add custom logic here ...
      // Be sure to call the base class's OnLoad method!
      base.OnLoad(e);
   }
}

public class WebForm1 : MyBaseClass
{
   private void Page_Load(object sender, System.EventArgs e)
   {
      // Put user code to initialize the page here
   }
   ...
}

Good Example of Inheritance

http://www.4guysfromrolla.com/webtech/022001-1.shtml

General Items

Getting Item from AppSettings

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Str_AppSettingValue = ConfigurationManager.AppSettings["app setting name"];

Getting current date and time as a string

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Str_DateTimeExample = DateTime.Now.ToString("yyyy-MM-dd HH:mm tt");

Format Operators

• d – Numeric day of the month without a leading zero.
• dd – Numeric day of the month with a leading zero.
• ddd – Abbreviated name of the day of the week.
• dddd – Full name of the day of the week.
• f,ff,fff,ffff,fffff,ffffff,fffffff -
• Fraction of a second. The more Fs the higher the precision.
• h – 12 Hour clock, no leading zero.
• hh – 12 Hour clock with leading zero.
• H – 24 Hour clock, no leading zero.
• HH – 24 Hour clock with leading zero.
• m – Minutes with no leading zero.
• mm – Minutes with leading zero.
• M – Numeric month with no leading zero.
• MM – Numeric month with a leading zero.
• MMM – Abbreviated name of month.
• MMMM – Full month name.
• s – Seconds with no leading zero.
• ss – Seconds with leading zero.
• t – AM/PM but only the first letter.
• tt – AM/PM ( a.m. / p.m.)
• y – Year with out century and leading zero.
• yy – Year with out century, with leading zero.
• yyyy – Year with century.
• zz – Time zone off set with +/-.

Examples of best practice guidelines

http://www.codeproject.com/Articles/118853/Some-Best-Practices-for-C-Application-Development

Class Design Patterns (Gang of Four)
http://www.dofactory.com/Patterns/Patterns.aspx